The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Engine speed sensors have typically been incorporated on the camshaft or crankshaft of the engine for providing accurate engine and transmission control. Encoder wheels are used in speed sensor devices to determine the rotational speed or position of a component. The encoder wheel typically includes an outer surface having magnetized ferrite therein. The ferrite can be magnetized to form alternating north and south poles around the circumference of the encoder wheel. In recent rotational speed sensing systems, active encoder wheels have been mounted to the end of the crankshaft, and an active or passive sensor is mounted in close proximity to the encoder wheel. The engine speed sensor of this type provides precise speed and position measurement for accurate misfire detection.
As the encoder wheel rotates, a magnetic sensor measures the change in the magnetic field of the alternating poles. From this alternating magnetic field, the rotational speed of the encoder wheel may then be calculated, and in turn the rotational speed of the component to which the encoder wheel is coupled is known.